Wal-Mart retakes the No. 1 slot on the Fortune 500 this year. See where America's largest corporations rank, and why.

Though revenues were up less than 2%, the tobacco king posted 15% profit growth last year. The world's largest cigarette maker saw a string of victories in tobacco lawsuits, and
spun off Kraft Foods in March. The former division is the world's second largest food and beverage maker, and accounted for nearly half of Altria's $70.3 billion 2006 revenue.